Process of producing cement and by-products



Patented Aug. 21, 1923.

UNITED STATES PATENT OFFICE,

FBEDEE ICK W. HUBER, 0F RIVERSIDE, CALIFORNIA, ASSIGNOB, BY MESNE ASSTGN- MENTJS, TO WESTERN PRECIPITATION COMPANY, A CORPORATION OF CALIFORNIA.

PROCESS OF PRODUCING CEMENT AND BY-PRODUCTS.

Ho Drawing.

To all whom it may concern:

Be it known that I, Fnnnmuorr /V. HUBER, a citizen of the United States, residing at Riverside. in the county of Riverside and State of California, have invented certain new and useful Improvements in Processes of Producing Cement and By-Products, oi which the following is a specification.

It is well known that in the calcination of Portland cement raw mix containing potassium compounds, :1 part at least of the potassium content thereof is yolatilized the calcining and clinkering operation. or operations, and processes have heretofore been proposed for the recovery of the so i olatilized potassium compounds, with the production of material as a hy-product suitable for the production of potash salts. In the prior art it has also been suggested to assist the volatilization of the potassium compounds from the raw mix, by the addition thereto of haloid' compounds, or other salts capable of assisting in the volatilization.

In accordance with the process of the present invention, I add to the cement making raw mix, sodium chlorid (i. e., common salt) in amount much more than that amount which would be equivalent to the K 0 content of the cement making raw mix. In computing the amount to be added, 1 part of K 0 is considered as being chemically equal to 1.2 parts of NaCl. In practice I have found that it is advisable to add, for each 1 part of K not less than about 2.4 to 3.6 parts of NaCl. In some localities the Portland cement raw material may be found to contain some sodium chlorid and this of course may be taken into consideration in computing the amount of sodium chlorid to be added. The raw mix. containing the sodium chlorid is then calcined and clinkered, for example in a rotary kiln heated by a counter current flame of powdered coal or other suitable fuel, and the waste gases or flue gases resulting from the operation, which contain in addition to a considerable amount of fine dust. substantially the entire amount of potassium in the original raw mix, are then treated for the recovery of the potassium compounds therefrom,

In the cement burning kiln, the material is heated to a temperature of approximately 1300-1400 (1.. in a current of gases, constituting the products of combustion of the Serial No. 205,870.

fuel, usually together with some air. The sodium chlorid there present at first reacts with the potassium compounds in the cement mixture, and the potassium compounds beiug less readil r volatile are vaporized. The use of the sodium chlorid or other volatilizing agent employed, in considerable excess over the amounts of potassium compounds to gases, in substantially the entire amount present in the raw mix.

The mixture fed to the rotary lgiln may he and is preferably ground to a fine powder, with the added salt, and this grinding may be effected by wet or dry grinding, in a manner well known in the art.

The continued heating of the cement making material in the elinkering zone, during and after the stage of liberation of the potassium compounds has a further effect in vaporizing the major part of the excess of sodium chlorid added, and th s excess of sodium chlorid when vaporized is likewise swept along by the flue gases. The flue gases leaving the kiln will accordingly contain three classes of materials, which it is necessary to consider in connection with the process of the present invention. These three classes of materials may be referred to as follows:

1. Flue dust containing particles of cemeut, particles of unburned or partially burned cement making raw material, coal ashes if coal be employed as the fuel, and other dust-like material in a solid state.

:2. Vaporized potassium compounds and potassium compounds which existed in the form of Vapor in the hottest Zone of the kiln, but which have partially condensed into the form of a fume.

gas washer.

as alxovc specified, arr then treated for the of course aili'isahle a1 ify these materials in tually separately obtain ltll'iiifl, or separate proi'lucis.

in pr u'tir'e I have ouu l the following iuethoil. forming a part oi the pre; ventioi to constitute a practical licieut, method of co: zlncting El e c and separation of the products. leaving the cement lriln which temperatnr. (a. temperature a or at a red heat, un te-r oriiliuc k ciuulitiOusX are first hrought into contact with water, in su-sa a manner as to considerably cool the r separate the major part 01" the (lust and coarser particles, and to ahsorh some ot the lame of alkali metal compounds. This operat on may be conducted by causing; the gase to pass through a gas s rubber. in which they aresuhjectcd to one or preieralily a pluality of water sprays, and in which the are causerl to rapirlly impinge upon liquiil in the bottom oi the washer. This operation is preferably conducted in a wa hor in whi h the gases pass over an-il unilcr hallle in staggered relotion water hein; placci'l in the bott m of the treating receptacle or washer, and water sprays or means tor producing thin sheets or films of water hip; provided, for example in the upper portion of such it is desirable in carrying out this part of the process, to allow the liquid to be with lrawn from the bottom of the gas washer and after more or less settling and sedimentation, to reintroduce such liquirl as a spray into tho gas washer, this serving to concentrate the. solution as regards sodium and potassium compounds. The temperature of the water coming out of this gas washer in practice may he close to the boiling point. This filjfii't'lllfin not only produces the effects ahove statc l. but also leaves the gases saturated with water vapor. The gases are then carri 'l t another washer in which they ar scruhhe l with wator, prcfcralily at a co iilerably lower to. perature. the wav r coming into the seconrl gas washer liciug prr t' ra zl t colil water. that is to say water at oril. wiry atn'i spheric hum perature. and th volume of water lieing so arljusteil as to allo the. iquirl to he removed from the as washer at a temperature of say about I... The liq fl collected in the first. washing apparatus. which may consist of a solution ui istantally saturated at the hoiling teiuw with socliun'i chlorirl anrl potas ch orirl, then drawn oft.

D .ring the iashin ii perati n. the portion at least. fllill the entire amount of the soiliuan suliaie anal potassium sulfate present. will have been converted,

spe i ie l, anil 1=l giiclcrelile, to class such a way as to eventhe three materials,

aturc major {which is largely derived by in eraction with the water and tree linuo. the flue lust into calcium ulfate wh ch only slightly soiuhl in water and "-ClilCll accordingly precipitated. in practice 1 have found that substantially the entire amount of the S0 content o the gases l ZOEU the cone of the, incl, aurl tion 0% the sulfur content the rolatilizatien or coznlruslion of the sul in: compounds. of the cement raw nix} is converted into calcium sulfate, the major portion of which settles out in the first washin; apparatus with the line (l, t.

The li uor is then pumpcrl oil" and is preferably conveyed, after filtration ii (lQSlF- ahle. or nece sary, to an evaporator. in which the liquicl is concentrate zl at or n the boillug temperature. first et o such concentration is to precipitate suhstanti: l Y

cnt therein ai'ter which the evaporation is continued at approximately the, hoil ng point. (luring which operation suhstautially the major portion of the s riium "lilflI'l(l separates or crystall ".es from the liquor. sodium chlorirl being: inatcriall less soluhle n hoi ing water, than pota sium cliloriil.

Aft r the liquor has lieer woui-entrr'ltml suiiiciently to separate the major portion of sodium chlorirl by crystallization. it is rlrawn oil to a. separate receptacle anrl is cooloil, whereupon potassium chlorirl rca lily crystallizes out. The liquor is further evaporatcch either at the hoiliug t mperature, or at a lower temperature, vf r the recovery of. the remaining potassium chlorirl constituent.

I call attention to the fact that at the curl. of the first evaporation step, the liquor cousi ts of a relatively pure solution of po -as siiin chlorirl, and accorrlin y the pots sium crystallized therefrom is @uhstantially pur especially the first crop oi crystals pl'iuliifl l by cooling the liquor.

The sodium chlorirl collecleil as allow il ser licrlhnrl alsoitilcsire l, the s mlc ol' l ic lust' coll ifterl in the g; washer may then he 21(lIlP l to the cement making raw ii'iatcrial, wherehy the process h eoznos cyclical a gartls the arlilition, eon-lensatiou. sepa ation an 'l reuse of the so liuu c. l.

Tlu use (it an ?iccs.- oi :i 'r'il c 1H1- tcr al (for er'an'rplr sodi m fl l inc to as ist in the i'olatilizaiiiu: oi th Nb 'wunils ron: at 1' och u -i' ricl ol :1 iur'oli amount. of he cement itself h werl to he a valor-hie un t 3*.

oeh iiio to The art- 'f p ash r on i w lll'h I am the first o 9 1.95; a procedur (iii) with the the t in th l iclic The we trec P nt o? tine Eases. a is alarm osciiliijil, crui li ll tl ro -F rm} in zle of op ration. loft. .ni'rnt u n t lllll restricted thereto. In some instances it may be advisable to precipitate the dust in a dry way, for example by electrical precipitation. The dust may then be agitated with hot wa ter to dissolve the potassium and sodium chlorids, the liquid separated from the sludge and the solution of potassium and sodium chloride Worked up as in the example above given, and the sodium chlorid reused in the process.

The flue gases, as above described, may pass directly from the kiln, that is to say from a housing surrounding the upper end of the kiln, into the first gas washer or saturator. I find it advisable, however, in ordinary practice, to pass the gases first through a cyclone dust collector, for the purpose. of separating from the gases, a considerable portion of the dust, before the gases pass into the first washer. The material which separates in such a dry dust collector is of course the coarser part of the solid matter, and it does not carry any apg'irciable quantities of potassium compounds, and may be reintroduced into the kiln without any further theatment.

The liquor coming from the second scrubber or condenser is a very much weaker solution, as regards solid matter, than the liquor coming from the first scrubber or saturator, In practice I find it advisable to allow the liquor coming from the second scrubber to pass to a cooling pond, in which the same is cooled down to ordinary temperature or to say C, after which it is pumped back and used as the spraying liquid in the second scrubber. The quantity of water used up in the system is of course also added in the second chamber.

A part of the liquor from the second scrubber is passed to the first scrubber, to make up for loss of liquor therein, both by evaporation, and to account for the quantity withdrawn for concentration and for separation of sodium and potassium compounds.

lVhat I claim is:

l. A process of making cement and byproducts which comprises heating to a clinker-forming temperature, a. cement mix containing potassiferous material and containing sodium chlorid in amount much more than equivalent to the amount of such potassifero-us ingredients, thereafter washting the flue gases with an aqueous liquid capable of removing at least the major part of the potassium compounds therein.

2. A process of making cement and by products which comprises heating to a clinker-forming temperature, a cement mix containing potassit'crous material and containing sodium chlorid in amount much more than cquvalent to the amount of such pot-assiferous ingredients, thereafter Washing the flue gases with an aqueous liquid capable of removing at least the major part of the potassium compounds therein, whereby a liquor containing sodium chlorid and potassium chlorid is produced, separating at least the major part of the sodium chlorid from such liquor, and thereafter separately separating the potassium compounds from said liquor.

3. A process of making cement and by products which comprises adding sodium chlorid to a potassiferous cement forming mix, in amount equivalent to not less than at least the amount of potassium compounds present, calcining and clinkering the mixture to produce cement and flue gases containing sodium compounds and potassium compounds, scrubbing said flue gases with an aqueous liquid in a plurality of stages, to produce liquids containing sodium and potassium compounds, and concentrating said liquor and separating sodium compounds from the heated liquor, and thereafter separating potassium compounds therefrom.

4. In the production of cement from raw materials containing potassium compounds, the step of heating a mixture containing such raw materials and containing sodium chlorid equivalent to not materially less than twice to three times the potash content 0f such raw materials, said heating being sufiicient to volatilize the at least major part of the potassium compounds, and thereafter recovering the potassium containing material driven oti in said heating operation.

5. In the recovery of values from cement flue gases containing sodium chlorid, potassium chlorid, and flue dust, the step of subjecting such flue gases to the action of an aqueous liquid, whereby sodium chlorid and potassium chlorid are absorbed from the gases and whereby the fiue dust is largely precipitated, and a reaction effected between the alkali metal sulfates and calicuni com pounds in said flue dust, and thereafter separating the sodium and potassium chlorids contained in said liquor.

6. The herein described process of obtaining a water-soluble potassium compound in the manufacture of Portland cement, which consists in mixing sodium chloride with the Portland cement mix, subjecting this mass to the direct action of the products of, combustion of coal whereby the sodium chloride is volatilized and becomes adapted to combine with a substantial portion of the ash contents of the coal, which portion is thereby prevented from combining with the soluble potassium compounds, collecting the dust which is given off by the mix, leaching the dust to separate, from the insoluble contents thereof, the soluble potassium compounds and the soluble sodium compounds. introducing the leached dust into the Portland cement mix in the next (wil ofihvprocess si'q'lamting out the SOhk bin puuzs mu ociunponn ls i'ronl the soluhiu ill Gd u lium guinlnl K; into the raw 1111?; in [he no. vjmio oi the yrowibs.

x o '2 Una harem [Ivan-men pz'owz s 01 ohirnmn; :1 'wzum' wlnhn: potassium compound in 2.11% manufacture of Portland cement,

contents whereby said ash contents is subsizml uliy pruvcnied from combining with tinsoiubiu potassium compounds, Poilmiing 1m dust which i given ofl' by said consi'imun is, leaching iho uiierteli 111% to sag umiu thervhmn ahe solubio potassium cornpounds and i110 soiubig sodium chloride. contained filol'uin, Lnt'z'wmcing tho i :zu'hmi (lust into the Portland cemvni; mix in Nut mail ("wrlo of the pmflws wpzuuiiing out Hm solul |u potassium (IUHIXHHiHliH from ([19 sodium chlorido, and intmduving 1h! separated Lhim'ido into the raw mix in ma m-xl cycle of the process.

In lostimony whereof 1' 111112; 1n higrmiure.

FhEDEHICL W. HUME 

